Variable output hydraulic pumps



Nov. 5, 1963 Filed Sept. 25, 1961 L. BAINES 3,109,378

VARIABLE OUTPUT HYDRAULIC PUMPS 4 Sheets-Sheet l |NVENTOR Les/[e Baines ATTORNEYS Nov. 5, 1963 L. BAINES 3,109,378

VARIABLE OUTPUT HYDRAULIC PUMPS Filed Sept. 25, 1961 4 Sheets-Sheet 2 FIG. 2.

INV'EQITOR [es/[e Ba mes ATTOQNEY Nov. 5, 1963 1.. BAINES VARIABLE OUTPUT HYDRAULIC PUMPS 4 Sheets-Sheet 3 Filed Sept. 25, 1961 lNvENToR [es/As flames Z/MZW $24 ATTORNEYS Nov. 5, 1963 BAINES 3,109,373

VARIABLE OUTPUT HYDRAULIC PUMPS Filed Sept. 25, 1961 4 Sheets-Sheet 4 s4 s3 9 gag g4 r o 6'6 5: 54

V /m as 5 2 62 55 I 0 m w/ A w lNvENToR Les/fa 5a/nes A TQRNEYS United States Patent 3,109 378 VARIABLE OUTPUT irrnnAULIc PUMPS Leslie Baines, Wakefield, England, assignor to Richard Sutclilfe Limited, Wakefield, England, a British comp y Filed Sept. 25, 1961, Ser. No. 140,398 Claims priority, application Great Britain Sept. 28, 1960 19 Claims. (Cl. 10337) This invention relates to variable output hydraulic pumps, and particularly to reciprocating piston pumps.

According to the present invention a variable output hydraulic pump includes a main piston reciprocable within a main cylinder, inlet means and outlet means for the main cylinder, an auxiliary cylinder having a piston mounted for free reciprocation therein and communicating with the head end of the main cylinder, and means for varying the stroke of the free piston.

Further, according to the invention, a variable output hydraulic pump comprises a plurality of main pistons reciprocable within a plurality of respective main cylinders, inlet means and outlet means for respective main cylinders, a plurality of auxiliary cylinder having pistons mounted for free reciprocation therein, respective auxiliary cylinders communicating with the head ends of respective main cylinders, and means for varying the stroke of each of the free pistons.

The, or each, auxiliary cylinder contains a further piston whose position within the auxiliary cylinder may be varied to determine the stroke of the free piston.

The stroke of the, or each, free piston may be varied between a value such that the whole of the output of its associated main cylinder during a working stroke of the main piston is discharged into the auxiliary cylinder and a value of Zero when substantially the whole of its associated main cylinder output is discharged through the associated output means. Conveniently the stroke of the, or each, tree piston may be set at any value between these two limits.

Conveniently, an auxiliary cylinder and free piston may form part of a unit which may be secured in communication with a main cylinder of a fixed output hydraulic pump so converting the latter to a variable output pump.

The, or each, main piston may be reciprocated within its associated main cylinder in any convenient manner, for example by a co-operating rotating cam or eccentric.

The invention will be more fully described and illusttrated, by way of example, with reference to the accompanying drawings showing variable output hydraulic pumps and, in which:

FIG. 1 is an end view and a part section on line AA ,of FIG. 2, and shows one form of pump,

FIG. 2 is a view partly in section on line BB of ,FIG. 1,

FIG. 3 is a part-sectional view on the line DD of ,FIG. 4, and shows another form of pump, and

FIG. 4 is a part-section on line C-C of FIG. 3.

The pump shown in FIGS. 1 and 2 comprises a casing 1, which constitutes an oil reservoir for the pump, having end covers 2 and 3. A camshaft 4 having cams 5 is supported within the casing 1 by roller bearings 6 mounted within a housing 7 secured to the casing 1 by cap screws 8 which also serve to secure the end covers 2 and 3 to the casing 1. One end of the camshaft 4 extends through the end cover 2, for connection to suitable rotary driving means, not shown; an oil seal 9 prevents oil leakage through the cover.

Each earn 5 carries a roller bearing assembly 10 which co-operates with a main piston 11 to reciprocate the latter within a main cylinder 13, formed in a cylinder block 13a, against the action of a spring 12 upon rotation of the camshaft 5. Each main cylinder 13 has an associated inlet passage 14, controlled by an inlet valve 15 which can open against the action of a spring 16,. and an outlet passage 17, controlled by an outlet valve 18 which can open against the action of a spring 19. The inlet valves 15 control the fiow of hydraulic liquid from within casing 1 via passages 20 and 14 to the main cylinders 13 whilst the outlet valves 18 control flow of hydraulic fluid from the main cylinders 13 to the outlet orifices 21.

Above each main cylinder 13 a housing 22 is secured to the cylinder block 13a by studs 23. Each housing 22 defines an auxiliary cylinder 24 which communicates via a passage 25 with the head end of its associated main cylinder 13. Within auxiliary cylinders 24 pistons 26 are mounted for free reciprocation therein. .Also mounted Within auxiliary cylinders 24 are control plungers 27 each having an inverted cup-shaped head 28, accommodating a spring 29, and a stem 30 of smaller diameter than the head 28, the stem being slidable within a portion of the auxiliary cylinder 24 of reduced diameter. 0 rings 31 maintain an oil-tight seal between the stem 30 and the walls of an auxiliary cylinder 24. The position of control plungers 27 within auxiliary cylinders 24 can be varied by means of rotatable cams 32 mounted in an upper portion 33 of the housings 22 and which co-operate with the control plunger stems 30, to determine the stroke of the free pistons 26.

Each piston head 28 has ports 34 communicating with a passage 35 in the housing 22, which passage is connected to the inside of casing 1 by a pipe 36. Each housing 22 also has a passage 37 at the bottom of cylinder 24 which is connected by pipe 38 to a further passage 39 formed in the housing 22 and communicating with the auxiliary cylinder 24 above the shoulder 40 of piston head 28.

The pump just described functions in the manner set out below; the description relates to the operation of the piston-cylinder assembly shown in FIG. 1 but it will be appreciated that the other piston-cylinder assembly, shown in FIG. 2, operates in a similar manner.

With cam 32 in the position shown in full lines in FIG. 1, an auxiliary cylinder 24 can receive the Whole output of its associated main cylinder 13 during a working stroke of the main piston 11 and the free piston 26 can travel through its maximum stroke. During the first suction stroke of the main piston 11 the inlet valve 15 opens and oil is drawn into cylinder 13 from Within casing 1 via passages 20 and 14 and free piston 26 is moved, with the aid of spring 29, to the lower limit of its travel within cylinder 24. During the pressure stroke of main piston 11 the free piston 26 is moved upwards until it abuts the control plunger 27 and oil is transferred from the main cylinder 13 to the auxiliary cylinder 24 via passage 25, the pressure exerted by spring 19 preventing outlet valve 18 from opening. During the following suction stroke of piston 11 the free piston 26 is again moved towards the main cylinder 13 thereby transferring oil from the auxiliary cylinder 24 back to the main cylinder 13, inlet valve 15 remaining closed. Thus, with cam 32 in this position a column of oil is alternately transferred between main cylinder 13 and auxiliary cylinder 24 and no oil is delivered to the output orifice 21.

If cam 21 is now rotated through to the position showh in broken lines in FIG. 1, the control plunger 27 moves the free piston 26 to the lower limit of its travel in the auxiliary cylinder 24. During a suction stroke of the main piston 11, inletvalve 15 opens and oil is drawn into main cylidner 13 via passages 20 and 14. During a pressure stroke of main piston 11 the free piston 26 cannot move upwards, since it is prevented from such movement by the control plunger 27 and cam 32, outlet valve 18 is opened against the action of spring 19 and oil is 'iee . is discharged through outlet orifice 21. In this position of cam 32 the pump output is a maximum.

With cam 32 rotated to a position intermediate of the two limiting positions described above, the free piston 26 will have a stroke intermediate the maximum and minimum (zero) strokes. In such a position, during a suction stroke of main piston 11 the free piston 26 is firstly moved to the lower limit of its stroke, inlet valve 15 then opens and oil is drawn into the main cylinder 13. During a pressure stroke of main piston 11 the free piston 26 is firstly moved to the upward limit of its stroke (determined by the position of control piston 27), by oil transferred from main cylinder 13 to auxiliary cylinder 24; when the movement of the free piston 26 is arrested by control plunger 27 the outlet valve 18 opens and the remainder of the oil in main cylinder 13 is discharged into outlet orifice 21.

It will be appreciated that the volume of oil discharged through the outlet orifice 21 will be determined by the stroke of free piston 26 and that this stroke, and hence the output volume, can be varied from zero to a maximum by suitable rotation of cam 32.

The connection between passages 37 and 39 ensures that the pressure required to rotate cam 32 during operation of the pump is minimised since pressure exerted on the underside of control plunger 27 is at least partially balanced by pressure applied to shoulder 40 of piston head 28.

The description above has related to a two-cylinder pump but it will be understood that a greater number of cylinders could be employed, if so desired.

The plunger 27, which determines the stroke of free piston 26, is shown in the drawings as being operated by a rotatable cam 32.

The pump shown in FIGS. 3 and 4 has a main pistoncylinder assembly somewhat similar to that shown in FIGS. 1 and 2 except that this latter pump is a 2-cylinder pump whilst the pump to be described is a 3-cylinder pump. In FIGS. 3 and 4 like references denote parts which correspond to those described with reference to FIGS. 1 and 2 and they co-operate in a similar manner. In FIGS. 3 and 4, however, the auxiliary piston-cylinder arrangement differs from that shown in FIGS. 1 and 2 and this modified arrangement will be described in greater detail.

Above the main cylinder block 13a is a cylinder block 51 having auxiliary cylinders 52 formed therein. The cylinder block 51 is secured to cylinder block 13a by studs 53and co-operating nuts 54 and the auxiliary cylinders 52 extend at right angles to the main cylinders 13 as is best shown in FIG. 3. Auxiliary cylinders 52 extend completely through the width of cylinder block 51 and are sealed at either end by closure members 55 and 56. The head end of each main cylinder 13 communicates with its associated auxiliary cylinder 52 via a passageway 57 which enters auxiliary cylinder 52 intermediate its ends.

On the right-hand side, as seen in FIG. 3 of the junctions between passageways 57 and their associated auxiliary cylinders 52, and within the auxiliary cylinders, are located free pistons 58 capable of slidable movement within respective auxiliary cylinders. The free pistons 58 are cup-shaped and within these free pistons are located springs 59 which extend into recesses formed in the closure members 56. These springs 59 urge their associated free pistons towards the left as seen in FIG. 3.

On the left-hand side of the junctions between the passageways 57 and their associated auxiliary cylinders 52, and withinthose auxiliary cylinders, are located control plungers 60 which at their right-hand ends, as shown in FIG. 3 have neck portions 61 of reduced diameter. The control plungers have drillings 62 which extend throughout their length and also have formed at their upper sides, as seen in FIG. 3, racks 63 which extend laterally across the plungers. Within chambers 64 formed in the cylinder block 51 and above respective control plungers 60 are pinions or toothed members 65 mounted for cooperation with the racks 63 of their associated control plungers 6b. The pinions 65 are secured by keys 66 on a common driving shaft 67 which extends through one end of cylinder block 51 via an oil seal 68. The protruding end of shaft 67 has a handle 69 whereby the shaft 67, and hence the pinions 65, can be rotated to slide the control plungers 66 within their auxiliary cylinders 52. The chambers 64 are covered by a cover plate 7 t) secured to the cylinder block 51 by cap screws 71.

It will be appreciated that by rotation of the shaft 67 the control plungers 60 can be moved between a position in which the movement of the free pistons 58 within the auxiliary cylinders 52 is prevented (i.e. their stroke is Zero) through intermediate positions to a position in which the free pistons 58 have maximum stroke in which the auxiliary cylinders 52 can receive the whole output of their associated main cylinders 13.

Passageways 72 connect auxiliary cylinders 52, intermediate the ends of control plungers 60 to the interior of housing 1 via the passageways 20.

The operation of the pump shown in FIGS. 3 and 4 will now be described with reference to the operation of the piston-cylinder assembly shown in FIG. 3, it being understood that the other two piston-cylinder assemblies shown in FIG. 4 operate in a similar manner.

In FIG. 3 the main piston 11 is shown at its top dead centre position and the control plungers 60 is shown intermediate its two limiting positions. As the cam shaft 4 is rotated piston 11 is urged from its top dead center position by the spring 12. and the spring 59 urges free piston 58 towards the control plunger 60 and any oil in auxiliary cylinder 52 is transferred via passageway 57 to the main cylinder 13. The inlet valve 15 then opens to admit oil from the interior of housing 1 into the main cylinder 13. On continued rotation of cam shaft 4 the main piston 11 is urged upwards, the inlet valve 15 is closed as is the outlet valve 18. During the pressure stroke of main piston 11 oil is initially transfenred from main cylinder 13 via the passageway 57 to auxiliary cylinder 52 and displaces the free piston 58 to the right against the action of spring 59. When the free piston 58 reaches the limit of its travel at which it abuts closure member 56, outlet valve 18 opens and oil is tnansferred from main cylinder 13 via the outlet passage 17 to the outlet orifice 19. V

The passageway 62 in the control plunger 60 allows oil to pass from the right-hand side of that piston to the left-hand side thereby equalising the pressure on either side of the control plunger. Thus there is no resultant force tending to rotate the shaft 67 and further, if it is desired to adjust the output of the pump, the shaft 67 can be rotated by means of the handle 69 with a minimum of effort. Any oil leaking from the left-hand side of control plunger 60 between that piston and the walls of the auxiliary cylinder 52 is returned to the interior of housing 1 via passageways 72.

By rotation of shaft 67 in an anti-clockwise direction, as seen in FIG. 3, the control plunger 60 can be made to urge the free piston 58 against closure member 56. In this position of the control plunger no oil is displaced from the main cylinder 13 to the auxiliary cylinder 52 during a pressure stroke of main piston 11 and the volume of oil transferred from main cylinder 13 to the outlet orifice 21 is a maximum. Rotation of shaft 67 in a clockwise direction, as seen in FIG. 3, moves control plunger 60 to the left until eventually it abuts closure member 55. In this position of the control plunger 60 the whole volume of oil contained in the main cylinder 13 is transferred to the auxiliary cylinder 52 during the pressure stroke of the main piston 11, the outlet valve 18 7 remaining closed. Under these conditions the output of whose pistons are reciprocated by a rotating camshaft.

Clearly, the invention is also applicable to other types of reciprocating pump, for example, swash plate, connecting rod or eccentric operated pumps.

1 claim:

1. A high pressure variable output hydraulic pump including a main cylinder having a head end, a main piston arranged for reciprocation in the main cylinder, pressure responsive hydraulic liquid inlet means and outlet means for the main cylinder, an auxiliary cylinder, means interconnecting the head end of the main cylinder with the auxiliary cylinder intermediate the ends thereof, resilient means mounted in the auxiliary cylinder on one side of the said interconnection, a control plunger mounted within the auxiliary cylinder on the other side of the interconnection, a free piston mounted in the auxiliary cylinder between the control plunger and the resilient means for axial movement therein, said control plunger constituting a stop means for limiting the movement of the free piston, means for adjusting the position of the control plunger for variation of the volume swept by the free piston as it moves within the auxiliary cylinder whereby the auxiliary cylinder receives hydraulic liquid from the main cylinder during a working stroke of the main piston in dependence on the adjustment of the control plunger, said received hydraulic liquid moving the free piston against the resilient means, and means for balancing hydraulic thrusts exerted on the control plunger during working strokes of the main piston.

2. A high pressure variable output hydraulic pump acn cording to claim 1, including a chamber which communicates with the auxiliary cylinder intermediate the ends of the control plunger, and adjustment means housed by the chamber for co-operation with the control plunger to adjust the position of the latter within the auxiliary cylinder.

3. A high pressure variable output hydraulic pump including a plurality of main cylinders having respective head ends, main pistons arranged for reciprocation in the respective main cylinders, pressure responsive hydraulic liquid inlet means and outlet means for respective main cylinders, for each main cylinder a separate auxiliary cylinder, means interconnecting the main cylinders with respective auxiliary cylinders intermediate the ends thereof, resilient means mounted in each auxiliary cylinder on one side of the said interconnection, each auxiliary cylinder having a control plunger mounted therein on the other side of the said interconnection and free pistons mounted between respective control plungers and resilient means for axial movement within the auxiliary cylin ders, the said control plungers constituting stop means for limiting the movement of the respective free pistons, means for adjusting the positions of the respective control plungers for variation of the volumes swept by the free pistons as they move within auxiliary cylinders whereby the auxiliary cylinders receive hydraulic liquid from the main cylinders during working strokes of the main pistons in dependence on the adjustments of the respective control plungers, said received hydraulic liquid moving the free pistons against the resilient means, and means for balancing hydraulic thrusts exerted on the control plungers during working strokes of the main pistons.

4. A high pressure variable output hydraulic pump according to claim 3, in which the auxiliary cylinders extend transversely of the main cylinders.

5. A high pressure variable output hydraulic pump according to claim 3, including a plurality of chambers which communicate with respective auxiliary cylinders, each chamber housing adjustment means for co-operation with the respective control plungers to adjust the position of the latter within the auxiliary cylinders.

6. A high pressure variable output hydraulic pump, including a main cylinder having a head end, a main piston arranged for reciprocation in the main cylinder, pressure responsive hydraulic liquid inlet means and outlet means for the main cylinder, a housing, an auxiliary cylinder defined in the housing, the auxiliary cylinder extending transversely of the main cylinder, means interconnecting the head end of the main cylinder with the auxiliary cylinder intermediate the ends thereof, resilient means mounted in the auxiliary cylinder on one side of the said interconnection, a control plunger mounted within the auxiliary cylinder on the other side of the interconnection, a passage extending through the control plunger in an axial direction, a free piston mounted in the auxiliary cylinder between the control plunger and the resilient means for axial movement therein, the said control plunger constituting a stop means for limiting the movement of the free piston, the said housing defining also a chamber which communicates with the auxiliary cylinder, adjustment means housed by the chamber and arranged in co-operating relationship with the control plunger for adjusting the position of the control plunger for variation of the volume swept by the free piston as it moves within the auxiliary cylinder between a minimum volume and a volume equal to at least the displacement volume of the main cylinder whereby the auxiliary cylinder receives hydraulic liquid from the main cylinder during a working stroke of the main piston in dependence on the adjustment of the control plunger, said received hydraulic liquid moving the free piston against the resilient means.

7. A high pressure variable output hydraulic pump according to claim 6, in which the control plunger has an axially extending rack formed thereon, and in which the adjustment means comprises a shaft rotatably mounted in the chamber, the shaft having a tooth. arranged for co-operation with the control plunger rack whereby rotation of the shaft moves the control plunger in an axial direction within the auxiliary cylinder.

8. A high pressure variable output hydraulic pump including a plurality of main cylinders having respective head ends, main pistons arranged for reciprocation in the respective main cylinders, pressure responsive hydraulic liquid inlet means and outlet means for respective main cylinders, a housing, for each main cylinder a separate auxiliary cylinder defined by the housing, the auxiliary cylinders extending transversely of the main cylinders, means interconnecting the main cylinders with respective auxiliary cylinders intermediate the ends thereof, resilient means mounted in each auxiliary cylinder on one side of the said interconnection, each auxiliary cylinder having a control plunger mounted therein on the other side of the said interconnection, each control plunger having a passage extending throughout its length, free pistons mounted between respective control plungers and resilient means for axial movement within the auxiliary cylinders, the said control plungers constituting stop means for limiting the movement of the respective free pistons, the said housing defining also a plurality of chambers communicating with the respective auxiliary cylinders, adjustment means housed by the chambers and arranged in co-operating relationship with respective control plungers for adjusting the positions of the respective control plungers to vary the volumes swept by the respective free pistons as they move within the auxiliary cylinders between minimum volumes and volumes equal to at least the displacement volumes of the respective main cylinders whereby the auxiliary cylinders receive hydraulic liquid from the main cylinders during working strokes of the main pistons in dependence on the adjustments of the respective control plungers, said received hydraulic liquid moving to the free pistons against the resilient means.

9. A high pressure variable output hydraulic pump according to claim 8, in which each control plunger has an axially extending rack formed thereon, and in which the adjustment means comprise a shaft extending through the chambers and mounted for rotation, in each chamber a toothed member secured to the shaft for rotation therewith, the toothed members arranged for co-operation with the racks of the respective control plungers whereby rotation of the shaft moves the control plunge'rs in an axial direction within the auxiliary cylinders.

10. A high pressure variable output hydraulic pump I according to claim 8, and including a camshaft mounted UNITED STATES PATENTS Brown Mar. 6, Paterson Dec. 2, Voit Mar. 27, Froehlich et a1 Oct. 22, Bessiere Aug. 2,

FOREIGN PATENTS Australia Dec. 4, Great Britain J an. 17,

Great Britain Oct. 26, 

1. A HIGH PRESSURE VARIABLE OUTPUT HYDRAULIC PUMP INCLUDING A MAIN CYLINDER HAVING A HEAD END, A MAIN PISTON ARRANGED FOR RECIPROCATION IN THE MAIN CYLINDER, PRESSURE RESPONSIVE HYDRAULIC LIQUID INLET MEANS AND OUTLET MEANS FOR THE MAIN CYLINDER, AN AUXILIARY CYLINDER, MEANS INTERCONNECTING THE HEAD END OF THE MAIN CYLINDER WITH THE AUXILIARY CYLINDER INTERMEDIATE THE ENDS THEREOF, RESILIENT MEANS MOUNTED IN THE AUXILIARY CYLINDER ON ONE SIDE OF THE SAID INTERCONNECTION, A CONTROL PLUNGER MOUNTED WITHIN THE AUXILIARY CYLINDER ON THE OTHER SIDE OF THE INTERCONNECTION, A FREE PISTON MOUNTED IN THE AUXILIARY CYLINDER BETWEEN THE CONTROL PLUNGER AND THE RESILIENT MEANS FOR AXIAL MOVEMENT THEREIN, SAID CONTROL PLUNGER CONSTITUTING A STOP MEANS FOR LIMITING THE MOVEMENT OF THE FREE PISTON, MEANS FOR ADJUSTING THE POSITION OF THE CONTROL PLUNGER FOR VARIATION OF THE VOLUME SWEPT BY THE FREE PISTON AS IT MOVES WITHIN THE AUXILIARY CYLINDER WHEREBY THE AUXILIARY CYLINDER RECEIVES HYDRAULIC LIQUID FROM THE MAIN CYLINDER DURING A WORKING STROKE OF THE MAIN PISTON IN DEPENDENCE ON THE ADJUSTMENT OF THE CONTROL PLUNGER, SAID RECEIVED HYDRAULIC LIQUID MOVING THE FREE PISTON AGAINST THE RESILIENT MEANS, AND MEANS FOR BALANCING HY- 